The brand new Mavic Cosmic Ultimate UST wheelset is billing itself as the ultimate choice for competitive riders. They’re purportedly at the intersection of high tech and tradition, so what’s the verdict? How safe and stable can carbon wheels really be? We paid a visit to Mavic’s HQ in France before joining them on Corsica to really put the wheels to test.
It’s no secret that Mavic know wheels–in fact, you can justifiably claim that they’ve even reinvented them time after time. Back in 1934 the world’s first aluminium rims rolled out of their factory. Since 2006 they’ve turned their attention to equipping the professionals, with the team of engineers in Annecy focusing on the interplay of weight, aerodynamics and rigidity. By incorporating their own UST tubeless system onto their top-end COSMIC CARBON ULTIMATE, they’re launching a race-ready, puncture-resistant wheelset that goes by the name Mavic Cosmic Ultimate UST.
Mavic Cosmic Ultimate UST – The concept
While many wheel manufacturers have their heads buried in disc brake designs, Mavic have been reinvigorating rim brakes, pursuing an objective of a lightweight, aerodynamic and stiff carbon wheel that’s both tubeless and comes with a carbon braking surface. This was naturally a challenge – given the heat that’s generated while braking, most brands decide not to even bother designing a clincher rim brake wheelset. It gets even more complex when you take tubeless rims into consideration; these have to be engineered meticulously so that the tire is precisely bedded onto the rim bed with zero chance of air escaping. With all these competing elements, Mavic set about overhauling the current rims on the COSMIC CARBON ULTIMATE.
At 40 mm deep, the rims on the new Cosmic Ultimate UST wheels are constructed with a 3k carbon fiber weave around a foam core. The interior rim width is 19 mm. According to Mavic, this particular foam core elevates the durability of the wheels and enhances their effectiveness of dealing with heat.
As we get the tour of the production facilities, Mavic explain that the braking material on their latest carbon wheels regularly heats up to over 220°C while braking. Such temperatures, they warn, could cause the material to bend or stretch, essentially creating a temporary change in the wheel’s diameter. As regular clinchers have greater tolerances, they’re able to deal with such fluctuations. However, tubeless systems rely on a much more stringent cohesion of the tire and rim sizes that really need to stay exact so that no air escapes. If a rim is affected by the heat, this can also affect spoke tension, which increases alongside the temperature. Then counter in the fact that even pumped-up tires compromise the spoke tension on the rims. When it comes to tubeless wheels, Mavic’s team have calculated a 10% increase in this effect when compared to regular tube clinchers.
Mavic’s hot-out-of-development, unidirectional carbon spokes declare to have met all of these challenges head on. Created through a special process (whose details have to remain a mystery–even to us), the full carbon spokes are bonded directly to the rims to create a super rigid construction that’s able to withstand all of the above influences. An advantage of this construction is that the rims are produced without spoke holes and therefore are completely airtight. Mavic reassured us that the Cosmic Ultimate UST wheels can be trued to a certain extent, but it remains to be seen how exactly this can be done.
Another evolutionary step ahead of the Mavic COSMIC CARBON ULTIMATE, the French brand have also revised the hubs on this new UST iteration. The hub body is now smaller and exclusively made of carbon, which results in lighter and more aerodynamic wheels. The rear wheel has an asymmetrical design to ensure that drivetrain influences are fed more efficiently from the hub to the rims. This evolution is most visible when comparing the spokes on the non-drivetrain side.
The Cosmic Ultimate UST rear wheel houses Mavic’s ID360 freehub body, which engages rapidly while pedalling and makes for a super efficient transfer of your power. Made of aluminium, this freehub body is both lighter than its predecessor and Mavic’s standard freehubs and able to increase the stiffness of the hub.
The braking surface of the Mavic Cosmic Ultimate UST has been laser treated to optimise the engagement of the brake pads – which, incidentally, are also fresh out of development. It’s a process that essentially strips away a bit of the resin and roughens the surface. In keeping with current standards, the new brake pads shouldn’t leave any yellow traces on the surface.
Mavic will exclusively launch the wheelset as a whole system, comprising wheel and tire. The 25 mm YKSION PRO UST tires, developed alongside Hutchinson, are the go-to tire for these rims, with each hoop weighing 260 g. Other models from different manufacturers are also compatible, but not strictly advocated by Mavic for these wheels.
Mavic Cosmic Ultimate UST – Test
Having launched thee MY Mavic app that determines a rider’s optimal tire pressure, the French brand have dangled an effective tool in front of future and current customers. In our case, the parameters were set as follows: Performance, Sunshine, 19 mm interior rim width, Tubeless, 74 kg rider weight, 6.9 kg bike weight. The app did its calculations and came out with a recommended 5.8 bar at the back and 5.4 bar at the front. Let’s go!
Having equipped the wheels onto the FOCUS IZALCO MAX, the stage was set to fully profit from these wheels and suss out their potential. Kitted with a Shimano Dura-Ace Di2 setup, this whole thing was screaming: fast!
The stiffness of the wheels translates well into efficiency and great accelerating. Even with the brakes so close to the rims, we didn’t hear them touching the pads. The Cosmic Ultimate UST wheels are equally as responsive when grinding slowly up a mountain pass as they are when shooting out of hairpins at speed. No momentum lost. With such a lively and agile wheelset, it’s clear that Mavic aren’t inviting anyone to ride easy. If anything, they’re screaming for you to sprint, get out the saddle and attack.
The Cosmic Ultimate UST wheelset deliver a great ride on the flat too. Per pair they weigh in at 1,310 g, which is a low weight but they come with the satisfying ability to hold speeds. The moderately deep profile 40 mm rims combined with their bladed spokes are remarkably forgiving when surprised by those oh-so-joyous cross-winds. Even when tucked, there’s no sense of nervousness with these wheels and they demonstrate how Mavic have really stepped up their game with these recent developments.
You’ll need to be aware that the combination of the low weight and rigid rims means that you’ll feel every perfection – and imperfection – in the road. Competitive riders will love the responsiveness, but some might argue they are a bit harsh. But as these are billed as their race-ready, top-end model, you’ve got to assume that anyone buying these knows how to a ride a bike well. Bike handling skills should be a prerequisite for anyone spending 3,500€ on a wheelset. But while it is a lot of dollar, we would argue that the accumulative money saved by a distinct lack of punctures could end up justifying this purchase. But who are we to speak?
The braking performance impressed us within seconds, and even on descents that lasted more than 10 km, this positivity didn’t fade. On a purely performance level, rim brakes don’t currently rival disc brakes but these are incredibly close–particularly in dry conditions and when it comes to modulation. In wet conditions, the braking surface needs to be dried in order to perform at their best. Mavic told us that a disc brake version is in the pipeline, which is very exciting and we’ll be holding our breath until then.
Pretty often there are days when you can put thoughts of comfort aside – and those are usually the days when you want to win. These wheels are designed for exactly that purpose, so their harsher ride is a result of their desire to win and perform. Would you turn down a shot at a podium?
Mavic Cosmic Ultimate UST – Conclusion
The Mavic Cosmic Ultimate UST is a wheelset for aspirational Grand Tour winners. With such stiffness and responsiveness, these are destined for competitive riders looking to improve their speeds even more. The harsh ride isn’t the most welcoming sensation for those who are less versed in bike handling. The design and production are well aligned with their high-end tag and these rim brake models display well-thought-out design features. A puncture-resistant upgrade tip, the Cosmic Ultimate UST have really piqued our interest – and our curiosity: our only question being, why on earth have this French brand focused so much on the rim brake?
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Words: Photos: Benjamin Topf, ASO
